Stereoscopic image display and alignment method thereof

ABSTRACT

A 3D filter includes a first area having a plurality of even numbered and odd numbered alternating lines, each line having an equal height, the even numbered lines formed with a first polarization characteristic, a first dummy line formed outside of the first area and adjacent to a first line of the 3D filter, the first dummy line having a height greater than a height of a single line, the odd numbered lines formed with a second polarization characteristic, a second dummy line formed outside of the first area and adjacent to a last line of the 3D filter, the second dummy line having a height greater than the height of a single line, the first dummy line formed with a polarization characteristic opposite to a polarization characteristic of a first line in the first area, and the second dummy line formed with a polarization characteristic opposite to a polarization characteristic of a last line in the first area.

This application claims the benefit of Korea Patent Application No.10-2010-0035184 filed on Apr. 16, 2010, the entire contents of which areincorporated herein by reference as if fully set forth herein.

BACKGROUND

1. Field of the Invention

This document relates to a stereoscopic image display and an alignmentmethod thereof.

2. Related Art

An image display device implements 3D images using a stereoscopictechnique and an autostereoscopic technique.

The stereoscopic technique uses binocular parallax images which producelarge stereoscopic effects, and may or may not have a corresponding setof lenses or eyeglasses for viewing by the user. In the type of systemusing eyeglasses, binocular parallax images are displayed on a directview display panel or by a projector by changing polarizationdirections. Alternatively, using temporal division, polarizationeyeglasses or liquid crystal shutter eyeglasses may be used to implementstereoscopic images. In the type of system not using eyeglasses, thestereoscopic images are implemented by dividing optical axes ofbinocular parallax images, where optical plates, such as parallaxbarriers, are provided at front and rear surfaces of a display panel.

To mass-produce the stereoscopic image display devices, it is necessaryto efficiently align a display device and a 3D filter, which is disposedon the display device and divides light from the display device intolight corresponding to left eye images and light corresponding to righteye images.

A method of aligning a parallax barrier with a display panel has beenproposed in Korean Patent No. 10-0709728, where separate eyeglasses arenot used. In this method, as shown in FIG. 1, two cameras CAM1 and CAM2disposed at a predetermined distance from the display panel 1 and fromthe parallax barrier 2, take stereoscopic images displayed on thedisplay panel 1. The display panel 1 and the parallax barrier 2 arerepeatedly realigned while checking the division state of left eyeimages and right eye images until reaching a predetermined alignmentreference state.

However, in a method of aligning a display panel with a 3D filter by aworker who views images displayed on the display panel based onluminosity, or in a method that determines whether or not stereoscopicimages are divided over a predetermined reference value in a systemusing two cameras, power data and test pattern data must be provided tothe display panel so as to display the images. Therefore, using suchrelated art alignment techniques, it is difficult to numericallyquantify the degree of alignment or misalignment, equipment cost ishigh, and productivity is low.

In a known method of aligning a display panel with a 3D filter in theeyeglass type stereoscopic image display device, a worker wearspolarization eyeglasses, drives a display panel placed at a certaindistance, determines an alignment degree between the display panel andthe 3D filter through luminosity, and repeats the above-describedoperation until images displayed on the display panel are properlyviewed. The assignee of the present application has proposed, in KoreanPatent No. 10-0939214, a alignment system and method of stereoscopicimage display devices which can automatically align the 3D filter withthe display panel in the eyeglass type and solve the problems disclosedin Korean Patent No. 10-0709728. In this method, alignment marks areformed in a display panel and a 3D filter, the alignment marks arechecked by a vision system, and thereby the display panel and the 3Dfilter can be aligned with each other without driving the display panel.Also, an alignment state can be quantified by checking an alignmentstate of the alignment marks.

The 3D filter may have a known tolerance or variation. In this case,because an accumulated error increases as the distance increase from thealignment reference positions (alignment marks) during the alignment ofthe display panel with the 3D filter, an alignment error accumulates. Asa result, up and down viewing angles in the stereoscopic image displaydevice may be narrowed due to the tolerance or variation of the 3Dfilter.

SUMMARY

According to an exemplary embodiment, a 3D filter includes a first areahaving a plurality of even numbered and odd numbered alternating lines,each line having an equal height, the even numbered lines formed with afirst polarization characteristic, a first dummy line formed outside ofthe first area and adjacent to a first line of the 3D filter, the firstdummy line having a height greater than a height of a single line, theodd numbered lines formed with a second polarization characteristic, asecond dummy line formed outside of the first area and adjacent to alast line of the 3D filter, the second dummy line having a heightgreater than the height of a single line, the first dummy line formedwith a polarization characteristic opposite to a polarizationcharacteristic of a first line in the first area, and the second dummyline formed with a polarization characteristic opposite to apolarization characteristic of a last line in the first area.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a diagram illustrating a method of aligning a parallax barrierin a related art stereoscopic image display device;

FIG. 2 is a diagram illustrating a stereoscopic image display deviceaccording to an embodiment of the invention;

FIG. 3 is a diagram illustrating an alignment system of the stereoscopicimage display device according to the embodiment of the invention;

FIG. 4 is a diagram illustrating an ideal alignment state of a displaypanel with a 3D filter when alignment marks are formed at one side edgesof the display panel and the 3D filter;

FIG. 5 is a diagram illustrating a poor alignment of the display panelwith the 3D filter due to tolerance of the 3D filter when the alignmentmarks are formed at one side edges of the display panel and the 3Dfilter;

FIG. 6 is a diagram illustrating a phenomenon where up and down viewingangles are narrowed due to the accumulated alignment error as shown inFIG. 5;

FIG. 7A is a plan view illustrating alignment marks formed at centralportions of longitudinal edges of the 3D filter;

FIG. 7B is a sectional view illustrating alignment marks formed atcentral portions of longitudinal edges of the 3D filter;

FIG. 8 is a diagram illustrating alignment marks formed at centralportions of longitudinal edges of each of the display panel and the 3Dfilter;

FIG. 9 is a diagram illustrating up and down viewing angle of astereoscopic image display device where the display panel and the 3Dfilter are aligned with each other using the alignment marks as shown inFIGS. 7A to 8;

FIG. 10 is a diagram illustrating a 3D filter according to anotherembodiment of the invention;

FIG. 11A is an exemplary diagram illustrating an image of the boundaryregions of the 3D filter in FIG. 10, taken by cameras;

FIG. 11B is an exemplary diagram illustrating an image of the boundaryregion of the 3D filter in FIG. 10, taken by cameras;

FIG. 12A is an exemplary diagram illustrating an alignment state of thedisplay filter shown in FIG. 7A and the 3D filter shown in FIG. 10; and

FIG. 12B is an exemplary diagram illustrating camera movement when the3D filter is aligned on the display panel.

DETAILED DESCRIPTION

Hereinafter, embodiments of the invention will be described in detailwith reference to the accompanying drawings. Like reference numeralsdesignate like elements throughout the specification. In the followingdescription, when a detailed description of well-known functions orconfigurations is determined to be unnecessary the understanding of theinvention, such description will be omitted.

In the following embodiments, alignment indicia portions are defined asreference position marking points for aligning a display panel and a 3Dfilter, and are formed in plurality in each of the display panel and the3D filter. The alignment indicia portions may be implemented byalignment marks and/or dummy retarder patterns like the followingembodiments.

Referring to FIG. 2, a stereoscopic image display device according to anembodiment of this document comprises a display 10, a 3D filter 20, andpolarization glasses 30.

The display panel 10 may be implemented by display panels of flatdisplay devices such as a liquid crystal display (LCD), a field emissiondisplay (FED), a plasma display panel (PDP), an electroluminescencedevice (EL), an electrophoresis display (EPD), and so on. Hereinafter,the display panel 10 will be described by exemplifying a display panelof the liquid crystal display.

The display panel 10 comprises a lower transparent substrate providedwith a thin film transistor (TFT) array, an upper transparent substrateprovided with a color filter array, and a liquid crystal layerinterposed between the substrates. In the lower transparent substrate, apolarization film is attached to the rear surface facing a backlightunit, and an alignment layer for setting a pretilt angle of the liquidcrystal is formed at a surface contacting with the liquid crystal layer.In the upper transparent substrate, a polarization film 11 is attachedto the front surface facing the 3D filter 20, and an alignment layer isformed at a surface contacting with the liquid crystal layer.

The lower transparent substrate is provided with data lines suppliedwith data voltages, gate lines (or scan lines) which intersect the datalines and are sequentially supplied with gate pulses (scan pulses)synchronized with the data voltages, TFTs formed at the intersections ofthe data lines and the gate lines, and pixel electrodes respectivelyconnected to the TFTs. The data lines are arranged in the longitudinaldirection (y axis direction) of the display panel 10 and the gate linesare arranged in the transverse direction (x axis direction) of thedisplay panel 10. The liquid crystal layer is driven by electric fieldsgenerated by the pixel electrodes applied with the data voltages andcommon electrodes applied with common voltages. The common electrodesare disposed on the upper transparent substrate in a vertical electricfield driving type such as a TN (twisted nematic) mode and a VA(vertical alignment) mode, and are disposed on the lower transparentsubstrate along with the pixel electrodes in a horizontal electric fieldtype such as an IPS (in plane switching) mode and an FFS (fringe fieldswitching) mode.

The display panel 10 displays data for 2D input images in a 2D modewhere data is not separated according to left and right viewing. Rather,in such a 2D mode, each pixel displayed corresponds to the imageexactly. The display panel 10 also displays left eye image data L andright eye image data R for 3D input images in the form of a line by linepresentation in a 3D mode. For example, as shown in FIG. 2, the left eyeimage data L may be displayed in odd numbered lines of the display panel10, and the right eye image data R may be displayed in even numberedlines of the display panel 10. The polarization film 11 is attachedbetween the upper transparent substrate of the display panel 10 and the3D filter 20. The polarization film 11 transmits only a linearlypolarized light, which is transmitted through the liquid crystal layerand incident on the polarization film 11.

The 3D filter 20 is attached onto the polarization film 11 of thedisplay panel 10. The 3D filter 20 shown in FIG. 2 exemplifies aretarder, which delays a phase of light by λ/4 using a birefringencemedium. The 3D filter 20 includes first retarder patterns 20Acorresponding to the odd numbered lines of the display panel 10 andsecond retarder patterns 20B corresponding to the even numbered lines ofthe display panel 10. Light absorption axes of the first retarderpattern 20A and the second retarder pattern 20B are perpendicular toeach other. The first retarder pattern 20A, which is aligned with andfaces the odd numbered line, converts a light from the odd numbered lineinto a light undergoing left-circular polarization (or right-circularpolarization). The second retarder pattern 20B, which is aligned withand faces the even numbered line, converts a light from the evennumbered line into a light undergoing right-circular polarization (orleft-circular polarization).

A left lens of the polarization eyeglasses 30 includes a polarizationfilter, which passes only a light having undergone left-circularpolarization (or right-circular polarization) therethrough, and a rightlens of the polarization eyeglasses 30 includes a polarization filterwhich passes only a light having undergone right-circular polarization(or left-circular polarization) therethrough. A viewer wearing thepolarization eyeglasses 30 views only left eye images with the left eyeand only right eye images with the right eye to sense images displayedon the display panel 10 as stereoscopic images. The viewer may view 2Dimages in the 2D mode without wearing the eyeglasses.

In order to align the display panel 10 with the 3D filter 20, two ormore alignment marks are formed in the display panel 10. Also, alignmentmarks are formed in the 3D filter so as to correspond to the alignmentmarks in the display panel 10.

FIG. 3 shows an alignment system of the stereoscopic image displaydevice according to the embodiment of this document.

In FIG. 3, the alignment system comprises a vision system, an imageanalysis unit 51, a controller 52, an alignment driver 53, and an xyθtable 54.

The display panel 10 provided with alignment marks 12 is placed on thexyθ table 54. The 3D filter 20 provided with alignment marks 22 isaligned on the display panel 10 in planar relation.

The vision system comprises two or more cameras 41 facing the alignmentmarks 22 in the display panel side, polarization filters 42 disposedbetween camera lenses and the 3D filter, and a camera transfer driver 55which transfers the cameras 41 in an x-axis direction and in a y-axisdirection, as shown in FIG. 3. The polarization filters 42 transmitspecific polarization light towards the cameras 42. The polarizationfilters 42 may be omitted. The camera transfer driver 55 drives atwo-axial robot or a two-axial guide equipped with the cameras 41 andmoves the cameras 41 in the x-axis direction or in the y-axis directionunder the control of the controller 52.

The image analysis unit 51 or controller performs analog-digitalconversion for data output from the cameras 41, and performs imagingprocessing for the digital data so as to clearly show images for thealignment marks. The controller 52 calculates an error between areference point and a center point of each alignment mark obtained bythe cameras 41 (axial misalignment). The controller 52 calculates anerror between center points of the alignment marks 12 formed in thedisplay panel 10 and center points of the alignment marks 22 formed inthe 3D filter and facing them. The alignment driver 53 moves the X-Ytable 54 where the display panel 10 is placed such that the error valuesfrom the controller 52 become “0.” The alignment driver 53 may beseparate from the controller 52 or may be combined into a signalcomponent. Note that the X-Y table may support and move either thedisplay panel 10 or the 3D filter 20, or both. It is immaterial to thescope of this invention which component is moved as long as thealignment error is minimized when the display panel 10 and the 3D filter20 are moved relative to each other.

The xyθ table 54 supports the display panel 10 under the display panel10. The xyθ table 54 moves the substrate of the display panel 10 in thex-axis and y-axis directions by the alignment driver 53 and rotates thedisplay panel in the 0 direction.

An alignment of the display panel 10 with the 3D filter 20 describedbelow may be performed in a state where the display panel 10 is notdriven.

FIG. 4 is a diagram illustrating an ideal alignment state of the displaypanel 10 with the 3D filter 20 when the alignment marks 12 and 22 areformed at one side edge of the display panel and the 3D filter. FIG. 5is a diagram illustrating poor alignment of the display panel with the3D filter caused by tolerance of the 3D filter when the alignment marksare formed at only one side edge of the display panel and the 3D filter.

If the 3D filter 20 is aligned with the display panel 10 with respect tothe alignment marks 12 and 22 formed at the upper ends of the 3D filterhaving no tolerance, as shown in FIG. 4, all the lines of the displaypanel 10 and the 3D filter 30 can be aligned with each other inaccordance with a design value without an alignment error. However,generation of errors in the 3D filter 20 is unavoidable in themanufacturing process thereof. In FIGS. 4 and 5, the reference numeral14 denotes an active region which displays 2D images and 3D images inthe display panel 10. The active region of the display panel 10 includespixels arranged in a matrix. The reference numeral 24 denotes an activeregion of the 3D filter 20, which corresponds to the active region 14 ofthe display panel 10 and in which the first retarder pattern 20A and thesecond retarder pattern 20B are alternately arranged in the longitudinaldirection.

When the 3D filter 20 having tolerance is aligned with the display panel10, if they are aligned with each other with respect to the alignmentmarks 12 and 22 formed at the upper end (or lower end) of the 3D filter20, and at the upper end (or lower end) of the display panel 10, due toaccumulation of an alignment error, the alignment error increases as thedistance increases from the alignment marks 12 and 22, as shown in FIG.5. When the alignment error increases relative to the position of thealignment marks 12 and 22, the up and down viewing angles for viewing 3Dimages are narrowed, as shown in FIG. 6. According to a preferredembodiment, to minimize an accumulated tolerance when the 3D filter 20is aligned with the display panel 10, as shown in FIGS. 7A to 8, thealignment marks are formed at central portions of opposite longitudinal(or lateral) edges of each of the display panel 10 and the 3D filter 20.Although the alignment marks are preferably located at the center of thecorresponding longitudinal or lateral edge, the alignment marks need notbe placed at the exact center or midpoint of the corresponding edges,and some variation may exist. For example, in one embodiment, thealignment marks may be located at substantially a midpoint, but may varyby about 15% of the total length of the lateral edge. For example, ifthe lateral edge is 50 cm in length, the exact midpoint is 25 cm from acorner, and thus the location of the alignment mark may be located atplus or minus 7.5 cm from the exact midpoint.

When the alignment marks 12 and 22 are positioned at the centralportions of the longitudinal edges and the vicinity thereof of thedisplay panel 10 and the 3D filter 20 as shown in FIGS. 7A to 8, if thealignment marks 12 and 22 overlap each other as designed to align thedisplay panel 10 with the 3D filter 20, it is possible to minimize anaccumulated value of alignment error which increases in the farther sidefrom the alignment marks in the stereoscopic image display device. Thisis because the alignment error is evenly distributed upwards anddownwards with respect to the alignment marks 12 and 22 as shown in FIG.8. Therefore, when the alignment marks 12 and 22 are formed at thecentral portion of the longitudinal or lateral edges of each of thedisplay panel 10 and the 3D filter 20, and the alignment marks 12 and 22overlap each other to align the display panel 10 with the 3D filter 20,the up and down viewing angles for viewing 3D images, as shown in FIG.9, can be widened in a horizontally symmetrical manner about a center ofa display screen.

FIG. 10 is a plan view illustrating another embodiment of the 3D filter20.

Referring to FIG. 10, the 3D filter 20 comprises first retarder patterns20A formed at the odd numbered lines PR#1, PR#3, . . . , PR#n−1, secondretarder patterns 20B formed at the even numbered lines PR#2, PR#4, . .. , PR#n, a first dummy retarder pattern 20C formed on the firstretarder pattern 20A positioned at the uppermost end, and a second dummyretarder pattern 20D formed under the second retarder pattern 20Bpositioned at the lowermost end.

The height (or width) of the first dummy retarder pattern 20C is set tobe greater than that of each of the first and second retarder patterns20A and 20B so as to be easily differentiated from the first and secondretarder patterns 20A and 20B in the active region. A polarizationcharacteristic of the first dummy retarder pattern 20C may be set to bethe same as that of the second retarder pattern 20B. The height of thesecond dummy retarder pattern 20D is set to be greater than that of eachof the first and second retarder patterns 20A and 20B so as to be easilydifferentiated from the first and second retarder patterns 20A and 20Bin the active region. A polarization characteristic of the second dummyretarder pattern 20D may be set to be the same as that of the firstretarder pattern 20A. Therefore, the first retarder patterns 20A and thesecond dummy retarder pattern 220D convert incident light into leftcircularly polarized light (or right circularly polarized light).

When the 3D filter shown in FIG. 10 is aligned with the display panel10, the cameras 41 of the vision system capture two or more boundaryregions A, B, C and D where the dummy retarder patterns 20C and 20D areseen along with the first and second retarder patterns 20A and 20B inthe active region. The polarization filters 42 disposed between thecameras 41 and the 3D filter 20 may transmit specific polarizationlight, for example, right circularly polarized light (or left circularlypolarized light).

If the upper cameras 41 capture the upper boundary regions A and Bthrough the polarization filters 42, since only the right circularlypolarized light or the left circularly polarized light enters thecameras 41 through the polarization filters 42, as shown in FIG. 11A, animage where the first dummy retarder pattern 20C and DUM1 and the secondretarder pattern 20B and PR#2 are seen bright, whereas the firstretarder pattern 20A is seen dark is obtained. In addition, if the lowercameras 41 capture the lower boundary regions C and D through thepolarization filters 42, since only the right circularly polarized lightor the left circularly polarized light enters the lower cameras 41through the polarization filters 41, as shown in FIG. 11B, an imagewhere the second dummy retarder pattern 20D and DUM1 and the firstretarder pattern 20B and PR#n−1 are seen dark, whereas the secondretarder pattern 20B is seen bright is obtained. Through this comparisonof the images obtained by the vision system, it is possible to reducethe accumulated alignment error and also to confirm the first and secondretarder patterns 20A and 20B aligned with the lines of the displaypanel 10 in a tilted state in the θ direction.

When the display panel 10 is aligned with the 3D filter 20, the centralalignment marks 12 and 22 may be used along with the dummy retarderpatterns 20C and 20D formed at the upper and lower ends of the 3D filter20. For example, as shown in FIG. 12A, an image of the boundary regionsA, B, C and D of the 3D filter is obtained using the cameras 41 and thepolarization filter 42, and an alignment state of the 3D filter 20 withthe display panel 10 is confirmed by analyzing the image, therebypreliminarily correcting the alignment state. Successively, as shown inFIG. 12B, an image of the central alignment marks 12 and 22 is obtainedby moving the cameras 41 in the y-axis direction, and thus the alignmentstate can be secondarily corrected.

The display panel 10 has been described mainly based on the liquidcrystal display in the above embodiment, but may be implemented usingany suitable flat display panel device, such as a liquid crystal display(LCD), a field emission display (FED), a plasma display panel (PDP), anelectroluminescence device (EL), an electrophoresis display (EPD), andso on.

As described above, according to this document, the alignment marks areformed at substantially the central portions of each of the 3D filterand the display panel, and the alignment marks overlap each other toalign the 3D filter with the display panel, thereby distributing anaccumulated tolerance upwards and downwards with respect to thealignment marks. As a result, it is possible to widen the up and downviewing angles of the stereoscopic image display device by minimizingthe amount of alignment error accumulated when the 3D filter havingtolerance is aligned with the display panel.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the scope of the principles of thisdisclosure. More particularly, various variations and modifications arepossible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A 3D filter comprising: a first area having aplurality of even numbered and odd numbered alternating lines, each linehaving an equal height; the even numbered lines formed with a firstpolarization characteristic; a first dummy line formed outside of thefirst area and adjacent to a first line of the 3D filter, the firstdummy line having a height greater than a height of a single line; theodd numbered lines formed with a second polarization characteristic; asecond dummy line formed outside of the first area and adjacent to alast line of the 3D filter, the second dummy line having a heightgreater than the height of a single line; the first dummy line formedwith a polarization characteristic opposite to a polarizationcharacteristic of a first line in the first area; and the second dummyline formed with a polarization characteristic opposite to apolarization characteristic of a last line in the first area.
 2. The 3Dfilter of claim 1, wherein further comprising: a plurality of displayalignment marks disposed along a first edge and a second edge of thedisplay panel and the 3D filter, respectively, the first edge beingopposite to the second edge, wherein two of the plurality of displayalignment marks are disposed at a midpoint along opposite lateral edgesof the display panel and the 3D filter.
 3. The 3D filter of claim 2,wherein two of the plurality of display alignment marks are located oncorresponding opposite lateral edges within a distance from an exactmidpoint of the lateral edge equal to plus or minus 15% of a length ofthe corresponding lateral edge.
 4. The 3D filter of claim 1, wherein thedisplay panel is a liquid crystal display, a field emission display, aplasma display, an electroluminescence display, or an electrophoresisdisplay.